Hydraulic transmissions are used in a wide variety of vehicles and other equipment to change the ratio of input shaft speed relative to output shaft speed. Conventionally, a high hydraulic pump unit and cooperating swash plate on the input side of the transmission interact to displace hydraulic fluid to an outside pump which in turn interacts with an output side swash plate in a manner to rotate the output shaft. The transmission ratio essentially depends on the fluid displacement ratio of the two pumps.
In standard hydrostatic pumps, a greater flow of hydraulic fluid creates a faster output transmission shaft rotation. Thus, as the ratio of input shaft speed approaches one to one with output shaft speed, the oil flow is greatest. However, this condition also results in many moving parts resulting in wear of the various components during the highest output of the drive.